For thermoplastic polymer materials, there is sufficient predictability in the melt stage during the molding process of the casting machine. Under the action of the molding pressure, the melt flows and fills the mold cavity. The fluidity is usually used to measure the melt. The ability of the body to fill the cavity. The fluidity is an important indicator of the processing performance of polymer materials, fluidity and viscosity are inseparable. Viscosity is essentially a macroscopic measure of the internal friction between substances. The smaller the viscosity, the better the fluidity and the easier it is to form. On the other hand, during the molding process of the casting machine, that is, under the action of the complex stress field (shear stress, compressive stress, tensile stress, etc.) and temperature field, the viscosity of the polymer material melt will change greatly. , The so-called rheology.
In the processing of polymer materials, the rheological process of polymer melts that involve large sites, such as the melt (or melt) of polymer melts in the processing of injection molding, extrusion molding, and spinning flow. Understanding and mastering these rheological properties is of great significance for formulating the correct polymer processing technology, developing and designing casting machines, polymer processing equipment, molding dies and process control that meet the processing requirements.
The polymer processing process is similar to the typical chemical unit operation process. Associated with mobilization, energy and quality transfer. Representative examples include extrusion molding (including fiber spinning and film extrusion), injection molding, and blow molding. However, due to the special nature of polymer material processing (such as viscoelasticity), the polymer processing process is usually much more complicated than the chemical unit operation process. A full understanding and mastery of polymer processing requires knowledge of many disciplines and engineering, such as polymer chemistry, non-Newtonian viscoelastic fluid mechanics, and it is usually accompanied by heat and mass transfer or chemical reactions. Understanding and mastering the relevant knowledge of these casting machines will be very helpful to the future operation of the casting machine or the solution of its problems.
